1/* Locale-specific memory comparison.
2
3   Copyright (C) 1999, 2002-2004, 2006, 2009-2010 Free Software Foundation,
4   Inc.
5
6   This program is free software: you can redistribute it and/or modify
7   it under the terms of the GNU General Public License as published by
8   the Free Software Foundation; either version 3 of the License, or
9   (at your option) any later version.
10
11   This program is distributed in the hope that it will be useful,
12   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14   GNU General Public License for more details.
15
16   You should have received a copy of the GNU General Public License
17   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
18
19/* Contributed by Paul Eggert <eggert@twinsun.com>.  */
20
21#include <config.h>
22
23#include "memcoll.h"
24
25#include <errno.h>
26#include <string.h>
27
28/* Compare S1 (with length S1LEN) and S2 (with length S2LEN) according
29   to the LC_COLLATE locale.  S1 and S2 do not overlap, and are not
30   adjacent.  Perhaps temporarily modify the bytes after S1 and S2,
31   but restore their original contents before returning.  Set errno to an
32   error number if there is an error, and to zero otherwise.  */
33int
34memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
35{
36  int diff;
37
38#if HAVE_STRCOLL
39
40  /* strcoll is slow on many platforms, so check for the common case
41     where the arguments are bytewise equal.  Otherwise, walk through
42     the buffers using strcoll on each substring.  */
43
44  if (s1len == s2len && memcmp (s1, s2, s1len) == 0)
45    {
46      errno = 0;
47      diff = 0;
48    }
49  else
50    {
51      char n1 = s1[s1len];
52      char n2 = s2[s2len];
53
54      s1[s1len++] = '\0';
55      s2[s2len++] = '\0';
56
57      while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
58        {
59          /* strcoll found no difference, but perhaps it was fooled by NUL
60             characters in the data.  Work around this problem by advancing
61             past the NUL chars.  */
62          size_t size1 = strlen (s1) + 1;
63          size_t size2 = strlen (s2) + 1;
64          s1 += size1;
65          s2 += size2;
66          s1len -= size1;
67          s2len -= size2;
68
69          if (s1len == 0)
70            {
71              if (s2len != 0)
72                diff = -1;
73              break;
74            }
75          else if (s2len == 0)
76            {
77              diff = 1;
78              break;
79            }
80        }
81
82      s1[s1len - 1] = n1;
83      s2[s2len - 1] = n2;
84    }
85
86#else
87
88  diff = memcmp (s1, s2, s1len < s2len ? s1len : s2len);
89  if (! diff)
90    diff = s1len < s2len ? -1 : s1len != s2len;
91  errno = 0;
92
93#endif
94
95  return diff;
96}
97